Method of applying components to circuitry boards



Jan. 25, 1966 R. R. POTTER ETAL 3,230,612

METHOD OF APPLYING COMPONENTS TO CIRCUITRY BOARDS Original Filed July '7, 1955 2 heets-Shee 1 IN NTOR.

R \TER ER 6 woo Fu R BY EoBcRT HHN 1966 R. R. POTTER ETAL METHOD OF APPLYING COMPONENTS TO CIRCUITRY BOARDS 2 Sheets-Sheet 2 Original Filed July 7, 1955 INVENTOR. RossnsR R. POTTER FM A An l 0 m B E o United States Patent 'thus formed. This application is a divisional application of the parent application, Serial No. 520,544, filed July 7, 1955.

In the art of manufacturing electronic assemblies or sub-assemblies by employing printed circuitry, the usual method of mounting electrical components and jumper leads to the circuitry board has been merely to fix the components to the panel by threading the component leads through the circuit board holes and bending or clinching the lead ends so as to fasten the component tightly against the circuit board surface. With the component thus clinched, the board is then dipped in a bath of molten solder whereby to reinforce the mechanical and electrical connection with solder. In connecting the ends of jumper leads to the board, the stripped ends of such leads commonly are threaded through appropriate holes and bent so that during the solder-dipping operation the insulation of the lead provides the necessary support on the top surface of the board.

Certain inherent disadvantages, however, stem from mounting components tightly against the face of the board. Poor circulation of air for those components, such as resistors, which tend to become heated in operation may result in component failure due to overheating. Moreover, for those boards which include printed circuitry on both faces, it is undesirable to have resistive components, being a source of heat, in direct contact with the more or less delicate metallic strips forming the printed circuitry.

In the connection of jumper leads it is especially important to provide a mechanical connection which has a high resistance to pushing, pulling or twisting Without relying on the bond between the underlying copper strip and the surface of the dielectric forming the body of the circuitry board. Any stresses placed on the jumper lead, when connected by the conventional method, which may occur dur ing assembly of the boards or through maintenance and testing of the electronic units formed thereby result in a direct strain on the copper bond of the printed circuit. Unless great care is taken, these stresses will result in stripping the copper from the face of the board.

Accordingly, it is an object of the present invention to provide an improved means and method for mounting electrical components to printed circuit boards.

Another object is to provide a means for mounting in spatial disposition components on printed circuit boards with a mechanical connection between the lead wires of the component and the board that lends stability to the connection both prior and subsequent to any solderdipping operation.

A further object is to provide a method for adapting component leads of a range of diameters to a uniform size, permitting standardization of the circuit board holes.

Still another object is to provide an adapter for electrical components which produces a uniform and reliable mechanical connection with a given size circuitry board hole throughout a relatively wide range of hole diameters as permitted by design tolerances.

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A still further object is to provide an adapter for component leads especially designed to enhance the flow of solder, through capillary action, up through the hole and around the component lead during the solder-dipping stage of circuitry board assembly.

Yet another object is to provide an adapter for electrical component leads which, upon insertion into a circuit board hole, leaves a predetermined maximum void space without reducing the mechanical stability of the connection.

Still another object is to provide an adapter for component leads which facilitates the insertion of the leads Within circuit board holes by automatic fitting machines in a mechanized assembly line.

These objects are, in general, attained by imparting a cuneate configuration of special design to the end portions of the component leads. Conveniently, such configuration may be obtained by cold-forging or crimping about the component lead ends a pro-formed sheet metal adapter which is, according to one embodiment of the present invention, generally U-shaped in cross-section and includes a trough from opposed side edges of which respectively extend a pair of upstanding ears adapted to be forced during crimping into tight engagement with at least a portion of the component lead. The adapter may be applied, for example, by crimping or shaping dies having die faces which converge toward the end of the lead so that for leads of varying diameter more or less of the metal composing the adapter and lead is extruded away from the lead end, thus forming the end'port-ion of the lead to precisely a uniform cross-section, independent of the original diameter of the lead, and tapering to a point substantially coaxial with the axis of the component lead. The free ends of the upstanding ears of the connector may be curled or deformed, if desired, about a tight radius leaving a space between the opposed inwardly curled ear faces between which an indentor may pass to form a groove in a wire. Upon insertion of the formed lead end in a circuit board hole, the wire groove, supplemented in part by the curled ears of the adapted and in part by the side walls of the hole, forms a capillary tube through which solder readily flows. In its final form the lead end portion is substantially rectangular in cross-section with the bottom side edges being relatively sharp so as to make firm contact with the side walls of the circuit board hole in accordance with the taper whereby to achieve a good mechanical connection.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description When taken in conjunction with the drawings in which there are shown and described several embodiments; it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention but are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings: 7

FIGURE 1 is a perspective view of the end portion of an electrical component lead formed in accordance with one embodiment of the present invention;

FIGURE 2 is a perspective view of a plurality of adapter members in strip form prior to their application to component leads to produce the lead end portion shown in FIGURE 1;

FIGURE 3 is a fragmentary sectional plan view illustrating the mounting of the lead end portion of FIG- URE 1 in a hole of a printed circuit board;

FIGURE 4 is a diagrammatic side view of an electrical component mounted on a printed circuit board during dipping of the board in a molten solder bath;

FIGURE 5 is a fragmentary view in elevation of a printed circuit board illustrating the mounting in a circuit board hole of a lead end portion according to another embodiment of the invention prior to soldering the connection;

FIGURE 6 is an enlarged view generally taken at lines 6-6 of FIGURE 5, but subsequent to soldering the connection;

FIGURE 7 is a view generally taken along lines 77 of FIGURE 6 and illustrating the formation of solder fillet in connection with the lead end portion shown in FIGURE 5;

FIGURE 8 is an elevational view of pre-formed adapter blanks in strip form which may be utilized to produce the lead end portion of FIGURE 5;

FIGURE 9 is a perspective view of a pre-formed blank shown in FIGURE 8;

FIGURE 10 is a perspective view of the adapter member shown in FIGURE 9 applied to the end portion of an electrical component lead;

FIGURE 11 is an exploded perspective view of the dies for crimping the embodiment of the adapter member shown in FIGURES 8 and 9;

FIGURE 12 is a sectional side view of the crimping dies of FIGURE 11 assembled and in an intermediate stage in crimping an adapter member about a component FIGURE 14 is a perspective view of a lead end portion in accordance with another embodiment of the present invention;

FIGURE 15 is a perspective view of an adapter member which may be utilized to produce the lead end portion of FIGURE 14; and

FIGURE 16 is a fragmentary sectional view of dies in an intermediate stage of operation for crimping the adapter of FIGURE 15.

Generally in the solder-dip method of effecting the electrical connections between the leads of an electrical component and the conductive strips of a printed circuit panel, after application of an appropriate fluxing agent, the component is mechanically set in the panel by threading the leads through the holes from which the conductive strips desired to be connected through the component radiate. As thus connected, the underside of the panel is dipped in a bath of molten solder whereupo-nsolder wicks between the lead and the side walls of the hole to provide the desired solder joint. Such operations are Well known in the art of processing printed circuit panels and they may be carried out manually, or desirably accomplished completely automatically, e.g., by a plurality of machines operating serially which assemble a complete electronic subassembly from a supply of circuit panels, leads and electrical components. Such machines typically comprise means for initial preparation of the panels and placing them on a conveyor along which is aligned a battery of machines for preparing and fitting to the panels each of the various electrical components comprising the electronic subassembly, the last stage in the assembly line being a solder-dipping operation.

In the following description reference will be made to the adaptation of our invention to use with printed circuit boards or panels such as are employed in the art of automatically pro-formed electrical circuitry, but it is to be understood that this application is selected by way of example and other applications will be apparent to those skilledin the art. Moreover, the reference to printed circuit boards specifically is not to be taken as limiting since the invention is equally applicable to the panels formed of any suitable dielectric material, and

any method of reproducing a circuit design on either the upper or lower surfaces, or both, may be employed, such as by painting, spraying, chemical deposition, die stamping, laminating, etc.

It is desirable, especially where conductive strips are printed on both surfaces of the panel, that the leads of the electrical components be set in the holes of the printed circuit board in a manner to support mechanically the body of the component away from the surface of the board both during and subsequent tothe solder-dipping stage in assembly. To provide such support, the end portion 1, FIGURE 1, of each of the component leads is shaped to have generally a cuneate configuration tapering toward the tip from a maximum transverse dimension at least equal to the diameter of the circuitry-board hole whereby the lead end portion may be mechanically .locked in the hole by a wedging action. As will be de- 7 scribed in connection with FIGURE 4, and lead 4, typically single stranded solid wires, when bent into a U-shape and anchored at tips 2 are contemplated to have sufficient rigidity to support the component body 3 off the face of board 5.

The cuneate form may conveniently be imparted to the lead ends by cold-forging thereon an adapter member 7 of a suitable malleable sheet metal stock, the cold-forging operation being performed through the use of die apparatus generally similar to conventional and well-known crimping apparatus for applying solderless electrical terminals and exemplified by Patent No. 2,692,422, issued October 26, 1954, to Frank L. Pierce, except that, as will be described in connection with FIGURES ll, 12 and 16, a longitudinal convergence is imparted to both the operating faces of the die parts. Adapter members 7, as pre-formed blanks in FIGURE 2, each may comprise a trough 9 having a pair of upstanding ears 11 extending from opposed side edges, with a connecting link 13 joining a pair or more of troughs in end-to-end strip fashion if desired.

Forming of adapter members 7 to the configuration shown in FIGURE 2 is accomplished by blanking and "forming techniques generally well-known in the art, and preferably from strip stock whereby a large number of elements may be joined as .a continuous strip rolled into a reel, thus to facilitate handling and subsequent application to component leads by automatic or semi-automatic crimping machines as will be referred to in connection with FIGURES 8 to 13. Prior to application of the adapters, the base metal composing the adapter strip is preferably plated with .a metal, such as tin, to which sold-er readily adheres. In contemplation of the soldering operation each adapter, conveniently while still in strip form, may have applied thereto a non-corrosive flux, for example, stearic Wax, which preferably also has characteristics rendering the fiux'capable of acting as a lubricating agent for the crimping dies during the crimping operation. In the crimping operation lead 4 is disposed Within trough 9 and ears 11 are curled under compression about and inwardly toward the lead to effect an intimate contact securely aifixing adapter 7 to the lea-d. Preferably the crimping die parts include a flat or slightly concave anvil Whereby the resultant crimp will be substantially rectangular in cross-section, FIGURE 3, having relatively sharp corners 16 along the bottom side edges with the upper surf-aces of ears 11 shaped to define a longitudinal groove 15 along the top.

In addition to providing for a wedg-ing action, tapering the crimp of adapter 7 facilitates insert-ion of lead end portion 1 within the circuitry board holes. This is especially advantageous where the components .are to be inserted by automatic means since the accuracy required of such means may be reduced proportionally with the sharpness of tip 2. Moreover, by maintaining the crimpheight, being defined by the degree to which the die parts of the crimping apparatus are closed, the Wide range of wire sizes encountered in mountin the'variety of electrical components utilized in printed circuit applications are advantageously reduced to a uniform size and shape at end portion 1 whereby standardization and uniformity of the circuit board holes may be achieved regardless of the diameter or character of the component lead. To this end the taper angle and crimp height are set so that the smallest diameter wire employed will just be sufficiently gripped to furnish adequate support for the component, and the maximum transverse dimension at the rearward end of adapter 7 is greater than the hole diameter with the length of adapter 7 being not significantly greater than the thickness of the circuitry board. For example, on a standardized 0.072 inch hole diameter, an included taper angle of 10 for a crimp 0.170 inch in length for boards in the range of 0.060 inch thickness will accommodate wire sizes from 0.020 to 0.047 inch in diameter. It will be understood, of course, that with a constant crimp height the smallest accepted wire will be engaged by cars 11 during crimping only over a limited length from tip 2 along the length of adapter 7, but as larger wire sizes are used, the etfective crimp length will increase until substantially a voidless crimp is had over the whole length of the crimped area. Larger Wire sizes than that in which the mass of metal included within the crimp length precisely matches the void space within adapter '7 may be used since any excess of wire metal will simply be extruded out of the crimp area back along the wire axis due to crimping on a taper.

Referring again to FIGURE 3, wedging end portion 1 Within hole 17 of circuitry board .19 causes corners 13 to bite into the sidewalls of the hole thus securely anchoring lead 4 in a manner such that stresses on the lead or component will be absorbed in the mechanical lock afforded by adapter 7 without transmission to or reliance on the strength of the bond between conductive strips 21 and board 19 prior or subsequent to soldering.

In the solder-dipping operation, to promote the wicking of solder through capillary action and formation of solder fillets on both the upper and lower surfaces of iboard 19 around end portion 1, whereby conductively to couple lead 4 with conductive strips 21, the configuration of end portion 1 in cross section relative to hole 17 .should provide as much void area as possible without adversely affecting the holding power of adapter 7 for the component lead. In the embodiment shown in FIGURES 1 to 3, the primary paths for the flow of solder are up along adapter 7 between its bottom surface and the side walls of hole 17, and along the top surface of adapter 7 and that port-ion of the side walls of hole 17 bounded by the tangential points of contact with curled ears 11, the closed boundaries of these paths defining capillary tubes having cross-sectional end areas indicated respectively at A and B in FIGURE 3.

Upon applying molten solder to the underside of the circuitry board, as by dipping the assembly in a solder bath, FIGURE 4, solder will rise in capillary tube-s A and B and on reaching the fluxed printed strip 21 ringing hole 17 will spread to form after hardening into a solder fillet. Solder will also cling to and harden on the metal surfaces on the underside of board 19 thus to form a fillet, or solder button, surrounding end portion 1 on both sides of board 19 as is shown and more particularly described in connection with FIGURE 7.

The method employed to crimp adapter 7 to the component lead is especially advantageous in that groove .15, formed by inwardly curled ears 11, increases the size of capillary tube B, thus enhancing the flow of solder in the solder-dip operation and ultimately the reliability of the electrical connection, by virtue of the solder, between lead 4 and strip 21. In the embodiment of FIGURES 1 to 3, however, the electrical qualities of the connection between lead 4 and strip 21 depend in large measure upon the effectiveness of the connection between lead 4 and adapter 7 since at best a relatively small surface area of the lead will be in direct contact with the solder.

Preferably, end portion 1 is formed so that solder comes in contact over a substantial area with freshly exposed surfaces of lead 4 thereby directly coupling strip 21 and lead 4. To this end, and to enhance the solder flow characteristics of capillary tube B, in the embodiment described in connection with FIGURES 5 to 10, a longitudinal passageway or groove 23 is provided along the upper surface of the lead end portion 27, FIGURE 10, which exposes lead 4 regardless of any adapter member which may be form-ed on the lead end portion. Advantageously, the upstanding ears of an adapter member form the passageway side walls and the component lead provides the bottom boundary, the dead preferably being impacted in the trough of the adapter member together with a coining action which exposes-fresh metal in the bottom of the groove. As shown, groove 23 extends substantially along the formed end of the lead which is coined or indented to a depth equal to approximately the center thereof at tip 29, the groove depth tapering away from the lead axis in accordance with the taper of'end portion 27 as best shown in FIGURE 7 and varying in depth of indentation according to the lead diameter of the component involved.

End portion 2 7, similar to end portion 1 of FIGURES 1 to 3, may conveniently be formed through utilization of an adapted member 31, FIGURE 9, which, in general, comprises a trough 33 for receiving lead 4 and upstanding cars 35 extending from the side edges of trough 33, ears 35 being adapted to be curled inwardly toward the lead in a manner to be described. Although the adapter-s may be separate pieces formed about the ends of the component leads by hand tools with the components thereafter being supplied to feeding machines in the circuit board assembly line, it is contemplated that the adapters will be be made in strip form, that is, connected in end-to-end fashion as by links 37, FIGURE 8. As thus connected, the adapters may be automatically fed and applied by standard applicator machines which may be made a part of the circuit board assembly line, such machines, except for the crimping section thereof, forming no part of the present invention and hence being omitted for purposes of simplicity.

The crimping die section, shown in exploded View in FIGURE 11, includes an upstanding generally rectangular column or post 39 which comprises the die anvil, the anvil being provided with a substantially flat die face 41 of a length slightly greater than trough 33. Post 39 projects from lower die block 43 which is rig-idly mounted on the fixed press bed, not shown, of the applicator machine. Upper die block 45 is provided with a recess formed by side walls 47 which are spaced to receive column 39 when the dies are being closed, FIGURE 13. The end of the recess approximates a W configuration with smoothly rounded bottoms formed by a pair of parallel cylindrical troughs 49 each of which is tangential to one of side Walls 47 and which unite to form a longitudinal ridge 5 1 along the center line of the recess. Upper die block 45 is mounted on and reciprocates with the movable ram, not fully shown, of the applicator machine. Also mounted on the applicator ram adjacent the rear sides of upper block 45 is a slug-out plate 53 having edges 54 Which sever from the strip the leading adapter upon its being disposed in the crimping area on die face 41.

On the front side of upper block 45 is mounted a guide plate 55 having a recess centered relative to the crimp- .recess and defined by side walls 57 and bottom 59.

Side walls 57 initially converge inwardly toward bottom 59 and serve to force leads 4 into alignment with the axis of trough 3 9 as the die parts move together. Bottom 59 of the guide recess is disposed slightly in advance of the crimping recess relative to the descent of the ram and serves to force the component lead into adapter trough 33 just prior to crimping, this action being especially advantageous where the lead diameter is near the upper end squeezed out of trough 33 during crimping.

desirable that the rear end edges of adapter 31 be crimped .of the applicator ram, advances the strip to position the leading adapter on die face 41 prior to the descent of die .block 45. As the ram and die block 45 approach lower block 43, guide plate 55 positions lead 4 in trough 33 as the slug-out blade severs link 37 from between the leading pair of adapters. Further descent of die block 45 initiates the curling of ears 35 around the contour of die troughs 49, ridge 51 turning the ends of ears 35 inwardly. As die block 45 continues its downward movement, ridge 51 maintains a separation between the ends of cars 35 which are turned slightly downwardly into lead 4. Ridge 51 effectively passes between ears 35 while curling the ear ends and, in the final portion of the downward stroke of die block 45, indents and coins lead 4 to form groove 23 and substantially a voidless crimp extending along the length of end portion 27 to a degree depending on the diameter of lead 4. To facilitate this curling action the outside ends of ears 35 are preferably beveled or swaged, as at 62, in the blanking process for fashioning the preformed strip.

The crimp, shown in cross-section in FIGURE 6, thus made results in an enlargement of capillary tube B which, on mounting the formed lead end in a circuit board hole,

comprises a portion of the side walls of hole 17, the ends of ears 35 and groove 23. The precise shape of tube B and groove 23 depend, of course, on the configuration of the recess in upper forming die 45. Advantageously, troughs 49 curl ears 35 about radii of curvature approximately equal respectively to one-fifth of the width of formed end portion 27, ridge 51 thus also being laterally equal to one fifth of the aforesaid width and depending 510.0'17 inch, included angle of die convergence;

for adapter 31, thickness of stock0.014 inch, radius of curvature of trough 33-0.016 inch, with cars 35 extending 0.115 inch above the base of trough 33 and an outside divergence of 0.100 inch at their ends. Similar dimensions for the embodiment shown in FIGURES 1 to 3 may be used except that troughs 49 would have a radius of curvature approximately equal to 27% the width of the crimp and converge to form a sharpcusp instead of the ridge as above defined.

From the foregoing dimensions, it will be apparent that on crimping adapter 31 about component leads having a diameter near the maximum size, a more violent extrusion of metal, both of lead 4 and adapter 3 1, will occur away from the point of convergence of the tapering die surfaces. To limit the extrusion of the metal of adapter 31 and to prevent the adapter from being forced wholly out of the crimp area, anvil 39 is provided with a lip 63 rising above the anvil surface thus forming a stop shoulder beyond which extrusion of adapter 31 may not occur. In addition, it is desirable, especially where small size leads are involved, that the inside surf-ace of the adapter member be provided with transverse serrations 64 which improve the gripping action near the forward end of the adapter thus to prevent the lead from being It is also square, that is, after forming, the rear edges should be perpendicular to the axis of lead 4 whereby to provide flat surfaces surrounding the lead of a width equal to the stock thickness on which an insertion tool or machine may conveniently operate to force the lead end into a circuit board hole. For this purpose the top edges of ears 35 are inclined downwardly toward the rear end of trough 33, FIGURE 8, to avoid the tilting of adapter 31 in the crimping dies which would tend to occur should upper die 45 first engage the adapter at the rear end of ears 35. Exemplifyi-ng, for a 10 convergence of the dies, a 17 inclination of cars 35 will suffice to assure a square crimp.

With adapter 31 thus formed about the end of lead 4, capillary tube in area and shape is adequate to insure the flow of solder in the solder-dripping operation. In this connection it will be understood that in designing a capillary tube, area is not the sole consideration. A long narrow slot, e.g., the openings bounded by the sides of adapter 31 and the hole side walls, FIGURE 6, has proven in practice to be unreliable in flow characteristics, the narrower the tube opening the less likelihood of achieving consistently good solder connections even though the area of the tube when translated into a circle would be suflicient under the conditions of use. On inserting end portion 27 in a hole with the rear of the adapter substantially flush with the board surface, groove or passageway 23, as shown in FIGURES 6 and 7 and formed with parts having the dimensions given above, provides a capillary tube having an end opening which roughly encompasses a rectangle at least 0.012 inch in width and 0.025 inch in height. Such dimensions have proven reliable under the exemplified conditions of use, a minimum workable width being approximately 0.010 inch at the groove bottom in contact with the lead and a height of about 0.024 inch. The minimum height and width relationships will be affected, however, by the conditions of use, that is, the solder composition as related to its flowability, the wetting characteristics of the solder flux, the degree of taper of the capillary tube, etc. For example, it has been found that the diameter of the larger opening at the bottom of the capillary tube which is essentially cone-like in shape inversely affects, due either to the physics of capillary flow or to greater entrapment of flux from the solder bath, the minimum diameter of the small opening at the other end of the tube.

Hardening of the solder after the solder-dipping operation results in the formation of solder fillets 65, FIG- URE 7, on both the upper and lower surface of the circuit board, directly connecting lead 4 at groove 23, with conductive strips 21. In this connection when the diameter of lead 4 is near the low end of the range of wire sizes, the crimping dies at the constant crimp height are effective to coin the lead only over a short length near the lead end. In this event the opening between ears 35 afforded by ridge 51 renders the interior of adapter 31, at approximately the point where the crimp ceases to be voidless, accessible to solder which may then flow along the lead within the adapter thus assuring continuous metal-to-metal contact over the length of lead 4 in the circuit board hole.

Upon forming of lead end portion 27, the components are contemplated to be fed automatically to the mounting machines in the assembly line, such machines effecting an automatic placement of the components in the appropriate holes in the circuit boards. To allow for such machines a maximum tolerance in the accuracy of the placement operation, the tip 29 of the formed lead should be as sharp as possible and coaxial with the lead. For this purpose anvil 39 is provided with an inverted V-shaped extension 67 which cooperates with a V-shaped groove 69 in slug-out blade 53 to shear link 37 from the body of adapter 31 so as to leave a V-shaped extension 71 integral with the front end of trough 33, FIGURE 10. To arrange the apex or point of extension 71 in alignment with the axis of lead 4, the plane of extension 67 of anvil 39 is inclined slightly upward relative to the plane of die face 41. To facilitate placement of the adapter body on anvil 41, that portion of link 37 in the pre-formed strip, FIGURE 8, which-is to form extension 71 is pre-bent relative to trough-33 in accordance with the inclination of anvil extension 67. For a dimensional example, in combination with the dimensions above referred to, a 12 inclination for anvil extension 67 relative to the place of die face 41 will align the point of a trough extension 71 having a length of 0.068 inch coaxial with lead 4 and cut at an included angle of 50. Preferably the lower portions of the front edges of ears 35 are provided with transition sections 72 which have a configuration to impart, on crimping the adapter, a tapering U-shaped crosssection to the trough extension in the region adjacent trough 33 whereby to avoid abrupt changes in the crosssection of end portion 27 that otherwise might tend to interfere with the insertion operation.

In the embodiment shown in FIGURES 5 through the component lead must be placed with some accuracy within trough 33 of adapter 31 to eifect optimum crimping, that is, the end of the component lead should be disposed near the foward edges of ears 35 in order to assure crimping of smaller diameter wires yet must not be inserted so far as to interfere with the formation of the pointed trough extension 71. In automatic application of the adapters this additionally requires accurate pretrimming of the leads. Advantageously, the leads are trimmed simultaneously with the crimping operation and the accuracy of the lead insertion rendered less critical. To these ends in the embodiment shown in FIGURES 14 to 16, the adapter member 73 is formed to permit insertion of lead 4 past the forward edges of ears 75 whereby in the shearing operation slug-out blade 77 severs strip connecting link 79 in a manner toform sharpened trough extension 81 and simultaneously trims lead 4 to have a pointed end 83 as best shown in FIGURE 14. In this connection the downward pressure exerted by slug-out blade 77 on the lead end during trimming is also advantageous in that in combination with guide plate 85, similar in function to guide plate 55 in FIGURE 11, lead 4 is positively forced into trough 87 from both ends of the adapter prior to curling car 75 during crimping regardless of the lead diameter. It will be apparent that the most extreme extrusion and coining of metal occurs at the forward end of the crimping dies. Inserting lead 4 to the extent required for trimming during crimping, however, adds to the metal which must be moved out of the critical forward portion of the dies. To reduce the mass of metal at this point the forward edges of cars 73 are notched as at 89 adjacent trough 87.

With the end portions of component leads formed in accordance with the present invention it will be apparent to those skilled in the art that the placement of the leads within the circuit board holes is facilitated and the flow of solder in the solder-dipping operation is enhanced resulting in a high quality mechanical and electrical connection to the board and to the printed conductive strips, with the components being advantageously rigidly and spatially disposed above the surface of the circuit board. It will be further apparent that the provision of the longitudinal groove in the formed lead end will promote the flow of solder by capillary action up through the circuit board holes along the component lead thence to contact the printed conductive strips of the surface of the circuit board, FIGURE 7, regardless of whether the conductive strips are extended to cover the side walls of the circuit board holes.

Obviously the formed end may also provide the means by which printed circuit jumpers may be mounted in the circuit board holes. Commonly, such jumpers are insulated with polyvinyl formal thermo-plastics, such as Formvar, which heretofore had to be initially stripped before electrical contact could be made with the printed strips of the board. According to the present invention,

however, Formvar leads can be utilized without prior preparation since in the soldering operation the solder will contact the wire core of the lead either at the trimmed tip, FIGURES 7, 10 and 14, or along the formed groove which, because of the violent deformation of the lead in the crimping operation, provides an area in which the Formvar insulation has been broken.

In addition, it will also be apparent that for lead end portions formed in accordance with the principles of the invention shown and described in connection with FIG- URES 5 through 16, the adapter band may be made of a low or non-conductive material since the metal of lead 4 through groove 23 is rendered accessible to solder regardless of the conductivity of the adapter member. Accordingly, the adapter member may be formed of sheet steel, or, if desired, may be of insulating material, such as nylon, pressed as a finished piece or die cast in place. Furthermore, if a sufficient mass of metal is present within the crimping region without the additional metal afforded by the adapter member, the end of the conductor alone can be cold-formed by the dies to the desired configuration.

We claim:

1. The method of conforming electrical leads of various diameters to a standard size hole of a printed circuit board or the like, including the steps of forming a series of adapter members joined in strip fashion by integral connecting links, disposing the end segment of a lead along the leading member of the series with the associated connecting link extending forwardly of the lead end segment, forming the member and end segment into tight engagement to a taper for adapting the lead to a wedge fit in the hole, and severing the connecting link intermediate its length along a plane inclined to the longitudinal axis of the lead to leave a lead-in pointed extension on the member.

2. The method of conforming component leads of various diameters to a standard hole size of a printed circuit board including the steps of disposing adapter material along the end segment of a lead of any diameter within the range of various diameters, the cross-sectional dimensions of the adapter being at least equal to hole diameter, cold-forming the adapted material and the end segment of the lead into a composite unit defining a lead end portion, reducing the tip or" the lead end portion to a constant non-circular cross-section of maximum lateral dimension less than the hole diameter, and reducing the rearward part of the lead end portion to a constant noncircular cross-section of maximum lateral dimension at least equal to the hole diameter.

3. In the solder-dip process of connecting the leads of electrical components to the conductive strips of a printed circuit board, the steps of mechanically applying to a lead an adapter member for frictionally fitting the lead to the holes of the board, forming a groove of capillary dimensions along the side of the adapter member, inserting the adapter member and lead in a hole of the board so that the capillary groove extends from one to the opposite side of the board, and applying molten solder to one side of the board to cause solder to flow up the capillary groove to the opposite side of the board for contact with conductive strips thereon.

4. The method of conforming electrical leads of various diameters to a standard size hole of a printed circuitry board or the like, including the steps of forming a series of adapter members joined in strip fashion by integral connecting links respectively, disposing the end segment of a lead along the leading member of the series with the end of the lead overlying the leading connecting link, forming the member into tight engagement with the lead to define therewith a composite lead end portion engageable with the side walls of the hole, and severing the connecting link intermediate its length through the overlying lead along a plane inclined to the longitudinal axis ofthe lead to .trim the lead to leave a lead-in pointed extension on the member for guiding thelead end portion .into the hole. a

5. The method of conforming electrical leads of various diameters to a standard size hole of a printed circuitry board or the like, including the steps of forming a channel-shaped adapter member, disposing a lead within and substantially along the length of the trough of the member, bending inwardly the opposed legs of the channel to form a ferrule in tight engagement about the end segment of the lead to define a lead end portion, the legs: being bent inwardly along a taper to provide for- ;ward and rearward portions with maximum transverse dimensions respectively less than and at least equal to the hole diameter for adapting the lead for wedge fit insertion in the hole, stopping the bending action short of closing the ferrule to leave exposed a longitudinal section of the metal of the lead for rendering the lead accessible to direct contact by solder.

6. The method of'mounting a lead of an electrical component in a substantially circular hole of a printed circuit board for electrical connection with a conductive strip radiating from'the hole, including the steps of forming an adapter member about and into tight engagement with a lead-to provide acuneate lead end portion tapering toward the lead end from a'maxirnum transverse dimension at least equal to the hole diameter, wedging the lead end portion into the hole from one side of the board, and

applying solder to the other side of the board to cause solder to flow upwithin the hole around the member and into-contact with the conductive strip.

7. The method of mounting the leads of an electrical component in electrical connection with the conductive strips of a printed circuit panel having substantially circular apertures from which the strips radiate, including the steps of forming a series of uniform channel-shaped adapter members for conforming the component leads to the aperture diameter and joined in strip fashion by connecting links, pressing the-lead of a component into the channel of the leading member of the series and forming at least the member to provide a lead end portion tapering toward the lead end from a maximum transverse dimension at least equal to the aperture diameter, forming a longitudinal groove in the lead end portion to provide a portion of a capillary tube, severing the leading member from the series, wedging the lead end portion in an aperture from one side of the panel, the aperture side wall op- 'and along substantially the length of the channels of the strips of adapter members, forming the end segments and adapter members into tight engagementto a taper of uni- I form dimensions to adapt the leads for a wedge-fit inser- I tion in the holes, .with each combined adapter member and end segment having'its insertion end reduced to a maximum lateral dimension significantly less than the hole diameter and its rearward part to lateral dimensions at least equal to the hole diameter regardless of the lead diameter; f

9. Themethod of mounting and soldering a lead of an electrical commponent in a circular hole of a printed circuit board for electrical connection with a conductive strip leading to the hole, including the steps of pressing the lead in and along a channel-shaped adapter member and shaping the member to provide a non-circular cuneate composite unit tapering toward the end of the lead from a transverse dimensionat least equal to the hole diameter to a maximum transverse dimension less than the hole diameter at the end of the unit, wedging the unit including the end segment of the lead Within the hole to leave an exterior surface of the unit along its full length within the hole in spaced opposed relation with thesidewall of the hole to define a capillary tube extending from one side to the other side of the board, and applying molten solder to one side of the board to, cause solder to flow Within the capillary tube to the other side of the.

board to connect the unit with the conductive strip.

10. The method according to claim 9 wherein the lead is left exposed through the open side of thechann'el to define at least part of the exterior surface providing the capillary tube with the solder directly contacting the lead as it flows in the capillary tube.

11. In the method of mounting and soldering a lead of an electrical component in a hole of a printed circuit board, the steps of placing the end segment of the lead in and along a channel-shaped adapter member and forming the member to provide a cuneate composite unit tapering toward the end of the lead to adapt the lead for Wedge-fit insertion in the hole, and cold-forming a longitudinal groove along the end segment of the lead through the open side of the channel to define at least part of a capillary tube for the flow of solder along the part of the unit insertable in the hole.

References Cited by the Examiner UNITED STATES PATENTS 2,175,759 10/1939 Olson.

2,502,291 3/1950 Taylor 29155.55 2,534,881 12/1950 Schroeder 174-84 2,618,234 11/1952 Armacost 29495 X 2,659,871 ll/1953 Berg 29-155.55 2,692,422 10/1954 Pierce 29155.55 2,748,456 6/1956 Berg 29-l55.55 X 2,781,577 2/1957 Smellie 29-495 X. 2,818,632 1/1958 Hammell 339276 2,839,824 6/ 1958 Berg- 29l55.55 X 2,893,009 7/ 1959 Bergsland et al 17468.'5 2,902,629 9/ 1959 Little et a1. 29155.5 3,059,152 10/1962 Khouri 29-1555 X WHITMORE A. WILTZ, Primary Examiner.

, JOHN F. CAMPBELL, Examiner. 

1. THE METHOD OF CONFORMING ELECTRICAL LEADS OF VARIOUS DIAMETERS TO A STANDARD SIZE HOLE OF A PRINTED CIRCUIT BOARD OR THE LIKE, INCLUDING THE STEPS OF FORMING A SERIES OF ADAPTER MEMBERS JOINED IN STRIP FASHION BY INTEGRAL CONNECTING LINKS, DISPOSING THE END SEGMENT OF A LEAD ALONG THE LEADING MEMBER OF THE SERIES WITH THE ASSOCIATED CONNECTING LINK EXTENDING FORWARDLY OF THE LEAD END SEGMENT, FORMING THE MEMBER AND END SEGMENT INTO TIGHT ENGAGEMENT TO A TAPER FOR ADAPTING THE LEAD TO A WEDGE FIT IN THE HOLE, AND SEVERING THE CONNECTING LINK INTERMEDIATE ITS LENGTH ALONG A PLANE INCLINED TO THE LONGITUDINAL AXIS OF THE LEAD TO LEAVE A LEAD-IN POINTED EXTENSION ON THE MEMBER. 